An example of how mushrooms and plants interact

Mycorrhizals are a symbiotic interaction between superior mushrooms and the roots of some plants (mostly trees). Plants use the expense network formed by the mycelium as a pathway of communication (hormones, nutrients...), so they can benefit other plants of the same species or damage other plants from other species. This has a huge impact on ecosystems (like forests) and also for agriculture.
You have an explanation of this in this video (although it is in Spanish) .
Enjoy!